Method 1. Mix the oregano, olive oil and half the chopped garlic together, add the chopped lamb and toss to coat. Cover and refrigerate for 2 hours or overnight if more convenient. 2. Preheat the grill to high. 3. Thread the lamb onto skewers (if using wooden skewers, soak these in water for at least 20 minutes beforehand) and grill for 8-10 minutes, turning occasionally, until done to your liking. 4. Meanwhile, make the tzatziki: combine the rest of the garlic, yoghurt, diced cucumber, finely diced onion and herbs and serve with the kebabs.